1. Field of the Invention
The invention relates generally to peripheral component interconnect (PCI) cards for personal computers and more particularly to a PCI card for receiving a global positioning system (GPS) signal.
2. Description of the Prior Art
A personal computer (PC) is commonly used to process location, navigation, and timing data provided by a global positioning system (GPS) receiver. The GPS receiver downconverts a GPS satellite signal, correlates the downconverted signal against a replica signal, and computes GPS-derived information for location, navigation, and timing information from the correlation signal. The GPS-derived data is then issued to the PC using a convenient data signal interface format such as RS232, RS422, PC104, or PCMCIA. The PC processes and displays the GPS-derived data in a form that is useful for an application.
Existing GPS receivers include one or more memory chips for storing correlation and computation firmware and a microprocessor for executing the firmware to correlate the GPS signal and compute the GPS-derived data. Such GPS receivers are conceptually straightforward because they are self-contained and the communication with the PC is simple and well-defined. However, the use of the memory chips and microprocessor in the GPS receiver is wasteful because the PC must include memory and processing power in any case. Further, due to the recent advances in custom GPS chipsets, the cost of the memory chips and microprocessor in the GPS receiver are a major portion of the cost of an entire GPS receiver. Unfortunately, little or no effort has been made to use the memory and processing power in the PC to reduce or eliminate the cost of memory chips and/or microprocessor in the GPS receiver because of the conceptual complexity of such GPS receiver and because the convenient data signal interface formats are too slow to pass the downconverted signal and/or the correlation signal between the GPS receiver and the PC.
Recently, a peripheral component interconnect (PCI) bus has been used to interface high speed signals between the PC and an embedded PCI card for full-motion video editing and serving. The PCI bus provides a data path capable of accessing up to 264 megabytes of data per second. In addition to being optimized for high bandwidth, the PCI bus also addresses cache coherency, multiple bus master support, and processor independence. Commercial PCI bus bridges are now available for interfacing to the PCI bus.